Progressive deep-drawing machine

ABSTRACT

Index-feed deep drawing apparatus comprising a feeding device for intermittently indexing a long-sized work piece, wound in a hoop, in the longitudinal direction, and a plurality of punch/die sets disposed in the feeding direction of the work piece and adapted to sequentially carry out deep drawing at least on the work piece, in which an annealing device adapted to allow the work piece to pass is provided between the deep drawing punch/die sets so as to subject the work piece to intermediate annealing treatment.

This application is a 371 PCT/JP98/00730, filed Feb. 24, 1998.

TECHNICAL FIELD

This invention relates to deep drawing apparatus used for deep drawingsheet stock, such as a steel sheet, into cup-shaped or bottomed hollowtubular products, and more particularly to index-feed deep drawingapparatus for sequentially deep drawing a long-sized work piece, woundin a hoop, in the longitudinal direction.

BACKGROUND ART

Deep drawing means are publicly known as means for forming cup-shapedcontainers, for example, from sheet metal. FIG. 4 is a partially cutawayperspective view of a typical process for forming cup-shaped containersusing a press mold. In FIG. 4, numeral 101 refers to a punch formed intoa cylindrical shape, for example, and vertically movably fitted to apress ram. Numeral 102 refers to a die formed into a hollow disc shapeor a hollow cylindrical shape and fitted to a press table in a coaxialmanner with respect to the punch 101. Numeral 103 refers to a blankholding pad formed into a hollow disc shape for pressing and releasing awork piece 104 onto and from a die 102 before and after the actuation ofa punch 101.

With the above arrangement, a disc-shaped work piece 104 having aninitial diameter, D_(O), for example, is positioned on the die 102 andforced onto the die 102 with a pushing force, Q, with the blank holdingpad 103. As the punch 101 is then forced onto the work piece 104 with adrawing force, P, the work piece 104 is deep drawn into a cup-shapedcontainer having a flange diameter, D. In this way, a metal formingprocess involving radial drawing of the work piece flange part 104a iscalled deep drawing. Deep drawing is a useful metal forming process forforming products having small wall thicknesses, such as cup-shapedcontainers, without generating a large amount of cutting chips asgenerated in machine working.

FIG. 5 is a longitudinal sectional view illustrating examples ofproducts formed with deep drawing; (a) being a bottomed hollow tubularproduct, (b) a hollow tubular one with a through hole on the bottom, and(c) a hollow tubular one. The cross-sectional shape of the product maybe a quadrangular, hexagonal, or other shape, in addition to a circularshape. The cross-sectional shape and dimensions may be varied atdifferent locations in the axial direction.

DISCLOSURE OF INVENTION

As noted above, deep drawing is a useful metal forming process having anadvantage that a long-sized product, having a large axial length sizecompared with the cross-sectional size, can be formed. When forming sucha long-sized product with a single drawing process, however, abnormallocal stresses tend to occur at various portions of a work piece 104,causing wrinkles and/or cracks. It is therefore a common practice tocarry out deep drawing in multiple steps. Carrying out deep drawing inmultiple steps, on the other hand, could accumulate work hardening,depending on the type of material used for the work piece 104, leadingto failure of predetermined deep drawing. To cope with this, it has beennecessary to anneal the work piece 104 in the middle of the deepdrawing.

In deep drawing involving multiple steps, multiple pairs of molds areusually needed; it has heretofore been a common practice that workpieces of a rectangular or disc shape blanked in advance in a separateprocess are individually charged on the mold manually, and the moldedproducts are also discharged from the mold manually. This involvestroublesome and dangerous operations, making it difficult to improveworking efficiency. For products of a small size, the complexity offorming operations would increase, leading to increased manufacturingcost.

Furthermore, annealing treatment to reduce or eliminate theaforementioned work hardening would have to be carried out in batches,increasing the amount of work-in-process in manufacturing processes.This would result in complicated process control and increasedmanufacturing cost.

It is therefore an object of this invention to provide index-feed deepdrawing apparatus that can solve the aforementioned problems inherent inthe prior art, and enables easy processing and highly efficientproduction.

To achieve the above objective, this invention adopts technical meanswhere a feeding device for intermittently indexing a long-sized workpiece, wound in a hoop, in the longitudinal direction, a plurality ofpunch/die sets disposed along the work-piece feeding direction forsequentially deep drawing at least the work piece, and an annealingdevice disposed between the punch-die sets in such a manner that thework piece is allowed to pass for intermediate annealing are provided.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1 and 2 are front and side views, respectively, of an embodimentof this invention.

FIG. 3 is a diagram of assistance in explaining the state where a workpiece is processed in an embodiment of this invention; (a) being a planview of a work piece being processed and (b) a longitudinal sectionalview of the work piece shown in (a).

FIG. 4 is a partially cutaway perspective view illustrating an examplewhere a cup-shaped container is formed using a press mold.

FIG. 5 is a longitudinal sectional view illustrating the shapes ofproducts being formed in deep drawing.

BEST MODE FOR CARRYING OUT THE INVENTION

FIGS. 1 and 2 are front and side views, respectively, of an embodimentof this invention. In FIGS. 1 and 2, numeral 1 refers to a feedingdevice, and 2 to a punch/die set; both provided on a base 3 in thefeeding direction of a work piece 4. That is, the feeding device 1 isadapted to intermittently index the long-sized work piece 4, wound in ahoop, in the longitudinal direction, and provided on the most upstreamside in the feeding direction of the work piece 4, for example. Thefeeding device 1, however, may be disposed on the downstream side of thepunch/die set 2, or between the punch/die sets 2 and 2.

The punch/die set 2 is such that an upper mold 7 is vertically movablyprovided via a guide bar 6 provided upright on a lower mold 5; the uppermold 7 being driven by a hydraulic cylinder (not shown), for example,via an actuating lever 8 so that the work piece 4 can be subjected todeep drawing and other forming operations.

On the upper and lower molds 7 and 5 provided are a pair of a punch 9and a die 10, respectively, for subjecting the work piece 4 to deepdrawing and other operations; a plurality of punch/die sets 2 beingprovided corresponding to required forming operations. The punch/diesets 2 are disposed at intervals of mP (m is a given positive integer,and P is an index feed of the work piece 4) in the feeding direction ofthe work piece 4, and the positions of the punch/die sets 2 can beadjusted in the feeding direction of the work piece 4 and the directionorthogonal thereto.

Numeral 11 denotes a high-frequency heating coil as a component of theannealing device. The heating coil 11 allows the work piece 4 to pass,and provided between the punch/die sets 2. Numeral 12 denotes a boothbar for supporting the high-frequency heating coil 11 and connecting thecoil 11 to a high-frequency power source 13.

FIG. 3 is a diagram of assistance in explaining the state where the workpiece is processed in an embodiment of this invention; (a) being a planview of the work piece being processed, and (b) a longitudinal view ofthe work piece shown in (a). In FIG. 3, numerals 21˜27 are processingsteps, comprising a pilot hole punching step 21, a first slitting step22, a second slitting step 23, a first drawing step 24, a second drawingstep 25, a third drawing step 26 and a punching and separating step 27.

A plurality of the punch/die sets 2 shown in FIGS. 1 and 2 are providedon the base 3 corresponding to the aforementioned processing steps21˜27. When installing this many punch/die sets 2, an adequate number(three units in FIG. 1) of punch/die sets 2 may be installed on a unit14, as shown in FIG. 1, and an adequate number of units 14 may beconnected in tandem in the feeding direction of the work piece 4,instead of disposing them on a single unit of the base 3.

In FIG. 3, the work piece 4 is intermittently indexed at intervals of apredetermined pitch, P, by the feeding device 1 shown in FIG. 1 in thedirection of an arrow shown in FIG. 1. Numeral 15 refers to a pilot holeprovided in multitude regularly at intervals of a predetermined pitch,P, on the work piece 4 by the punch/die set 2 on the most upstream sideshown in FIGS. 1 and 2 in the pilot hole punching step 21. The pilotholes 15 serve as reference holes in positioning the work piece 4 in thesubsequent steps.

In the first slitting step 22, pilot pins (not shown) are engaged withthe pilot holes 15 to position the work piece 4 in the punch/die set 2(the same applies to the subsequent steps), and then acircular-arc-shaped slit 16 is provided. In the second slitting step 23,another slit 17 is provided in the same manner to form apseudo-disc-shaped blank 18 on the work piece 4.

The work piece 4 is further indexed in the direction shown by an arrow,subjected to the first and second deep drawing steps 24 and 25, with anadequate number of idling steps intervening therebetween, to form a cup-or cap-shaped formed piece 19. Numeral 20 refers to a connecting parthaving a small width to connect the formed piece 19 and the work piece4.

Upon completion of the first and second deep drawing steps 24 and 25,work hardening takes place on the formed piece 19. Further deep drawing,with work hardened parts left as they are, may cause wrinkles and/orcracks on the formed piece 19.

To reduce or eliminate work hardening, the work piece 4 is passedthrough a high-frequency heating coil 11 for intermediate annealingtreatment.

Since the formed piece 19 connected to the work piece 4 via theconnecting parts 20 is softened in this intermediate annealingtreatment, further deep drawing can be carried out smoothly in the thirddeep drawing step 26 to form a formed piece 19 having a predeterminedshape and size. That is, the existence of the connecting parts 20 havinga small width prevents the heat of the formed piece 19 being deep drawnfrom being transferred to the work piece 4 having a large heat capacity.As a result, only the formed piece 19 can be heated. The connectingparts 20 are cut off in the final punching and separating step 27 topunch and separate the formed piece 19.

In the embodiment described above, the deep drawing operation is dividedinto three steps, but it may be divided into an appropriate number ofsteps, depending on the material type, shape, dimensions, etc. of thework piece 4. The intermediate annealing treatment may be interposedbetween most suitable processing steps, taking into considerationdrawing ratio and other factors in deep drawing.

INDUSTRIAL APPLICABILITY

This invention having the aforementioned construction and operation canaccomplish the following beneficial effects.

(1) Since deep drawing can be carried out continuously in an indexingmode, all manual operations for charging and discharging work piecesinto and from molds can be completely eliminated. Thus, deep drawnpieces can be produced easily.

(2) Since intermediate annealing treatment can be carried outautomatically in the middle of deep drawing operations, with formedpieces connected to the work piece, production can be accomplished withhigh efficiency.

(3) Even formed pieces having small dimensions may be transferredbetween different processes in a state where they are connected to awork piece, not as independent and separate pieces. This results in avery small amount of work-in-process, easy transportation and asubstantial reduction in manufacturing cost.

We claim:
 1. Index-feed deep drawing apparatus comprising a feedingdevice for intermittently indexing a long-sized work piece, wound in ahoop, in the longitudinal direction, and a plurality of deep drawingpunch/die sets disposed in the feeding direction of said work piece andadapted to sequentially carry out deep drawing at least on said workpiece, and an annealing device adapted to allow said work piece to passtherethrough is provided between said deep drawing punch/die sets so asto subject said work piece to intermediate annealing treatment. 2.Index-feed deep drawing apparatus as claimed in claim 1 wherein saidannealing device is a high-frequency heating coil.
 3. Index-feed deepdrawing apparatus as claimed in claim 1 wherein said feeding device isprovided on the most upstream side in the feeding direction of said workpiece.
 4. Index-feed deep drawing apparatus as claimed in claim 1wherein said punch/die sets are arranged so that formed pieces afterdeep drawing are connected to said work piece via connecting partshaving a small width.